Matched set of golf clubs and method of producing the same

ABSTRACT

The present invention provides a matched set of golf clubs, wherein each club in a set of golf clubs, irons, woods, or a combination thereof, provides the golfer with precisely the same feel, related to the golfer&#39;s swing when the club is swung, and to the contact between the head of the club and golf ball when the ball is hit. In the present invention the clubs are matched dynamically. The clubs with one or all of the following characteristics: (1) a constant flexural rigidity of each complete iron and/or each complete wood, (2) a substantially constant moment of inertia, and (3) a verifying center of gravity which is calculated by using a constant force for the shortest club in the set.

[0001] This is a File Wrapper Continuation of Application Ser. No. 09/540,393 filed Mar. 31, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to providing a matched set of golf clubs or flexuarally momentized golf clubs and more particularly to a set of golf clubs that all have the same feel when used by a golfer by rending each club to include at least one of the following: the same flexural rigidity, substantially a constant moment of inertia, and varying calculated center of gravity all of which are matched to the specific swing of the golfer who will use them.

[0004] 2. Description of the Prior Art

[0005] For years, golfers have relentlessly tried to improve their game by searching for the ideal set of clubs wherein each club “feels” the same. As such, numerous methods have been formulated in attempting to match a set of clubs to the user.

[0006] One such method which has proven to be successful is disclosed in U.S. Pat. No. 5,879,241 issued to Cook et al. In this patent, matching is accomplished by three criteria for each club, specifically providing a set of clubs with a constant flexural rigidity for each complete iron and each complete wood, substantially constant moment of inertia, and calculated varying center of gravity. Uniquely combining at least two of the three criteria produces favorable and successful results.

[0007] In the method described above, a process for providing a set of golf clubs with the same flexural rigidity is disclosed. In this process, it is desired to have equivalent frequency per club, that is, the shaft in combination with the head. In order to obtain this same frequency, the club (shaft and head) is placed on a conventional frequency analyzer at the desired length. The frequency is measured. If the frequency is not the desired frequency, the head is removed and the tip of the shaft is cut. This is known as tip cutting.

[0008] Though this method is ideal, this step is silent to other procedures and processes that can be utilized for producing a club with a constant frequency. Accordingly, it is seen that there exists a need for producing a club set with a constant frequency. Having a constant frequency will aid in ultimately producing a match set of clubs. The present invention achieves this intended purpose by providing additional methods, which may be advantageous to the manufacturer for achieving a set of clubs with a constant frequency. This present techniques identified herewith are new, useful and unobvious over prior methods thereof. The use of the present method is simple, cost effective, and one which utilizes a minimal amount of working components in order to successfully obtain constant frequency.

SUMMARY OF THE INVENTION

[0009] The present invention relates to providing a golfer with a matched set of golf clubs, wherein each club in a set of golf clubs, irons, woods, or a combination thereof, provides the golfer with precisely the same feel, related to the golfer's swing when the club is swung, and to the contact between the head of the club and golf ball when the ball is hit. In addition this method will focus on utilizing different methods for matching frequency within a set of clubs.

[0010] It has been discovered that this method of matching the frequency can be used alone, or can be combined with other steps for ultimately providing a set of golf clubs which are matched to a user for ultimately improving the game of the user. This matched frequency is a criteria for ultimately providing for a club to have the “same feel” and can be combined with matching the substantially constant moment of inertia of each club within a set and/or calculating a varying center of gravity that is matched to the specific swing of the golfer who will use them. Each criteria can be used alone or optionally can be combined in order to optimally provide for a matched set of golf clubs.

[0011] This method of matching frequency includes various embodiments. Each embodiment is tailored and customized to the need of the user and individuals matching the clubs to the player.

[0012] In the first embodiment, the shafts would be manufactured at different lengths in order to provide for a pre-cut blank for each club in the set. Once the head is installed on the first end of the shaft, the club is cut at the butt end of the shaft, known as butt-cutting, for obtaining both the required length and frequency for each club. In this first embodiment, the distance from the top of the hosel to the first step on the shaft would be virtually constant. The object of cutting is to obtain a constant frequency for each club within a set (woods or irons).

[0013] A second embodiment of the present invention is directed to shafts that are manufactured with varying lengths of the first step. For this arrangement, the method for successfully providing a set of clubs with a constant frequency is to butt-cut the shaft to the desired length once the head has been installed. This will provide the required length and frequency for each club in the set.

[0014] For shafts that do not have steps, a third method is disclosed. In this method, a constant frequency is obtained by cutting the butt end for the required length for each club of each set.

[0015] In the methods defined above, the frequencies can be altered, as desired, by changing and adjusting the head weight of each club. In this arrangement, increasing the head weight lowers the frequency, while decreasing the head weight increases the frequency. Alternatively, the frequency can also be adjusted, in all of the embodiments defined above, by either tip-cutting or butt-cutting the ends as deemed necessary. Tip-cutting has previously been address as indicated in the “Description of the Prior Art” in U.S. Pat. No. 5,879,241 issued to Cook et al.

[0016] Alternatively, some manufacturers produce shafts that are pre-cut to a specific length. In this situation, the desired frequency is obtained as defined above.

[0017] It is noted that the methods defined herewith are well suited for using parallel or tapered tip shafts. The methods as defined herewith have been used on both parallel and tapered tip shafts to produce favorable and successful results.

[0018] In addition to matching the frequency, the golfer may optionally have the substantially constant moment of inertia about the golfer's wrist mathematically calculated. This will aid in obtaining maximum distance a golfer can obtain by fitting the club with the proper maximum head weight. This maximum head weight will aid in achieving the maximum club head speed for achieving the maximum distance.

[0019] Establishing a center of gravity for each club will also aid in providing a matched set of golf clubs. Having a more ideal center of gravity for each club will render it to perform in a constant manner and will additionally provide constant feel between each club.

[0020] Accordingly, it is the object of the present invention to provide for a matched set of clubs and method of producing the same which will overcome the deficiencies, shortcomings, and drawbacks of prior dynamically matched golf club sets and methods thereof.

[0021] Another object of the present invention is to provide for a method for providing a set of golf clubs with substantially at least one of the following: the same frequency, the same substantially constant moment of inertia, and varying calculated center of gravity all of which are matched to the specific swing of the golfer who will use them.

[0022] It is another object of the present invention to provide for a matched set of clubs, wherein each club in the set provides the golfer with precisely the same feel.

[0023] Yet another object of the present invention is to replace the shafts of an existing set of golf clubs so as to allow each club of the set to have the same feel.

[0024] Still another object of the present invention, to be specifically enumerated herein, is to provide a matched set of clubs in accordance with the preceding objects and which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide clubs that would be economically feasible, long lasting, properly customized and relatively trouble free in operation

[0025] The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and application of the intended invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, a fuller understanding of the invention may be had by referring to the detailed description of the preferred embodiments in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is an enlarged side view of an assembled golf club illustrating a club having a tapered tip.

[0027]FIG. 2 is an enlarged assembled side view of a golf club illustrating a club that does not include a step.

[0028]FIG. 3 is a diagrammatic side view of a golf club illustrating the parameters used in calculating the center of gravity for each club.

[0029]FIG. 4 is a side view of a golf club in a balance state and illustrating the center of gravity.

[0030]FIG. 5 is a side view of the various shaped shafts and tips that are currently and commercially available.

[0031] Similar reference numerals refer to similar parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The present invention provides a set of golf clubs, such as irons, woods, or a combination thereof, which are synchronized for matching the particular swing of a particular golfer. This will provide for a set of customized clubs, which will inherently improve the game of the user.

[0033] As seen in the drawings, a golf club 10 can include various configurations for the shaft 14. For example, the shaft can be designed to include steps (illustrated in FIG. 5) or can be designed without the use of steps (FIGS. 1-4). This feature is merely a design element and is a personal choice that is deemed to be appropriate by the golfer, himself.

[0034] Each club, as seen in FIGS. 1 and 2, is provided with a head 12 having a head weight M_(h) and a shaft 14 having a shaft weight M_(s). The shaft 14 further includes a tip or first end 20 and a butt end 16. A grip 18 is attached to the butt end 16 and a hosel 24 of the head 12 is attached to the first end 20 of the shaft 14. The golf club 10 further includes a total length L that encompasses the head and shaft. The shaft 14 includes a shaft length L_(s), which encompasses the tip or first end 20 and the butt end 16. This butt end combined with the grip has a weight M_(b).

[0035] It is noted that the tip 20 can include a plurality of configurations, which are currently being manufactured. A few examples of tips that are commercially available are illustrated in further detail in FIG. 5. As seen in this drawing the tips can include a parallel configuration (20 a), a tapered configuration (20 b), or a combined parallel and tapered configuration (20 c). Note that FIG. 5 illustrates only a few tips that are available and that the design of the tip is deemed to be a matter of design choice and one which is dependent upon the brand, type and manufacturer that is used for fabricating the particular shaft. The object of the present invention is not the shape of the shaft or tip, but rather is a system that optimizes the performance of the golfer by altering the shaft of the golf club, regardless of the shape and configuration of the shaft and/or tip of the conventional golf club. This system has proven to be successful with all types and configurations of golf clubs, regardless of the structure of the shaft and/or tip as well as the material utilized to fabricate the club, including the shaft, handle and/or hosel.

[0036] For optimizing the performance of the golfer, three characteristics of the conventional golf club are taken into consideration. These three characteristics include: (1) a constant flexural rigidity of each complete iron and each complete wood, (2) a substantially constant moment of inertia for each iron and each wood, and (3) a varying calculated center of gravity as it relates to the swing of the individual golfer. For providing a set of flexuraly momentized golf clubs at least one of the characteristics must be met. The determination of each characteristic is discussed as follows:

[0037] Frequently—Flexural Rigidity

[0038] For optimizing the performance of the golfer, continuity within each club of a set is desired. One criteria that is extremely important is the frequency of each and every club. To understand frequency, the term flexural rigidity must be defined.

[0039] Flexural rigidity relates to the stiffness of the shaft of a particular golf club. To maintain a constant frequency, the flexural rigidity of the completed club must remain constant. Accordingly, within each set of clubs, the frequency must be the same. Hence, each club in the set of irons will have the same flexural rigidity and each club in a set of woods will have the same flexural rigidity. However, the flexural rigidity between the irons and woods may not necessarily be the same.

[0040] This flexural rigidity is related to the way that the golfer swings the club; therefore, the frequency difference between Irons and Woods depends on the particular golfer being fitted. Experience has shown that if the golfer repeats the same swing with the Irons and Woods the difference in frequency between Irons and Woods will be 30 cpm, with the Irons having the higher frequency. This is in contrast to the normal procedure, used in the golf industry, which makes the frequency of each club in the set different so that the shorter clubs are stiffer (higher frequency) than the longer clubs in the set. The term Flexural Rigidity and Frequency are in effect synonymous terms, with Frequency indicating a more precise definition of the exact stiffness of club required by the golfer.

[0041] The process for providing a set of golf clubs with the same flexural rigidity is of the utmost importance. In order to accomplish this, the shaft, including the head, provides for the particular club to have the same frequency. The shaft, without the head, may not have the equivalent frequency of the other clubs in the set. It is the combination of the head and shaft which makes up the equivalent frequencies, thereby providing one of the aspects for making each club in a set to have the same feel.

[0042] Shafts generally have different shapes and configurations. The most common being a shaft with a first step or a shaft without steps. These shafts can be tapered or parallel in tip structure. Along with the varying shapes, manufactures that produce shafts for golf clubs will transport them in a variety of forms.

[0043] This final form of the shaft is of the utmost importance, because it will determine which method is ideally suited for establishing the proper frequency.

[0044] Clubs come in a variety of pre-determined lengths. These lengths are common and well known. Once a length has been established, frequency must then be addressed, so that all the clubs of a particular set will all have the same frequency.

[0045] Establishing the correct frequency and having the same frequency for each club of each set is very important.

[0046] The process described above is continued with each club per set. The frequency of each club, with the head attached thereto, in a set of irons is within the range of 260 to 345 cycles per minute, while the frequency of each club, with the head attached thereto, in a set of woods is within the range of 230 to 300 cycles per minutes. It is noted that within each set of clubs, the frequency may be off by approximately plus or minus 1 cycle per minute, due to the added weight of the conventional attaching means for securing the head to the tip or first end of the shaft. However, this additional weight provides for such a minute alteration in the frequency that the actual feel for the user of the club is not affected.

[0047] For determining the appropriate frequency or flexural rigidity for a particular golfer, a set of preset test clubs is used. These preset test clubs all have the same head weight, shaft weight, swing weight, substantially constant moment of inertia, grip size and total weight. The only variable with these test clubs is the frequency. Typically and preferably, the 7 irons, 5 irons, and drivers are used in testing. Accordingly, each test club is built to a predetermined frequency such that the set of test clubs covers the full range of available frequencies. The difference in frequency from one test club to another should not exceed 5 cycles per minute.

[0048] Hence, for the determination of flexural rigidity, the golfer hits a series of balls with the preset set of test clubs. The user chooses the frequency from the club that felt the best and produced the best results. This method will allow precise determination of the frequency or flexural rigidity. If the user cannot decide between two separate frequencies with two separate clubs, i.e. 290 cycles per minute (cpm) with the 7 iron or 285 cycles per minute (cpm) with the 5 iron, then the test clubs can be choked, via conventional methods, for stiffening and increasing the frequency, for inherently determining the precise frequency. Each ¼ inch choke down is equivalent to an approximate increase of 2 cycles per minute (cpm). An example for this type of situation is discussed below in example 3. Other methods, such as allowing the golfer to draw or fade the ball can also be utilized in combination with the choking process, when the golfer has selected two separate frequencies for two separate clubs. This situation is discussed below in example 4.

[0049] The single most important element of a golf club is the stiffness of the shaft that is used for constructing the club. This stiffness, also known as the flexural rigidity, must be constant throughout a particular set (i.e. irons, woods, or a combination thereof) for providing consistency in performance from the clubs. For determining the optimum flexural rigidity for any shaft, the user or golfer of the club uses a flexural rigidity test means. This test means allows the user to determine the appropriate stiffness of the club for their particular swing. This correct stiffness provides the best feel and most consistent results. The proper feel obtained by the golfer in combination with the structure of the club will work simultaneously for improving one's game in golf.

[0050] Moment of Inertia

[0051] For determining the substantially constant moment of inertia, the user hits with preset test clubs. These preset clubs have predetermined set shaft stiffness and frequency. Ideally, the golfer should be fitted with the heaviest head that will provide the highest speed. Testing has shown that the ideal constant moment of inertia is directly related to the club head speed accomplished by the golfer during testing (Tables I and II are used when test clubs are not available).

[0052] Through years of testing various golfers of diverse skill levels, tables, labeled as Table I (for men) and Table II (for women), have been formulated. For tabulating the tables, a random selection of at least 900 people (at least 800 men and at least one hundred women) were tested. The testers took a series of golf clubs, having varying head weights, and hit a series of golf balls. The results were plotted on a graph of speed versus head weight. From the graph it was determined the best head weight to be used for a particular speed. The tables illustrate the results, which are used as standardized tables for men and women. TABLE I TABULATION FOR MEN Speed (MPH) utilizing a Distance (Yards) Swing Weight Driver Utilizing a 5 Iron Maximum Ideal 110 and up 205 and up C5 C2-C3 105-110 200-205 C6 C3-C4 100-105 190-200 C7 C4-C5  95-100 180-190 C8 C5-C6 90-95 170-180 C9 C5-C6 85-90 160-170 C9 C6-C7 80-85 150-160 D0 C7-C8 75-80 140-150 D0 C8-C9 70-75 130-140 D0 C8-C9 under 70 120-130 D0 C9-D0

[0053] TABLE II TABULATION FOR WOMEN Speed (MPH) utilizing a Distance (Yards) Swing Weight Driver Utilizing a Driver Maximum Ideal  95-100 See Men's Chart 90-95 See Men's Chart 85-90 See Men's Chart 80-85 180-190 C5 B7-B9 75-80 170-180 C6 B9-C2 70-75 160-170 C7 C2-C4 65-70 150-160 C8 C4-C6 60-65 140-150 C9 C6-C8 55-60 130-160 C9 C7-C8 50-55 120-130 C9 C7-C8 45-50 110-100 C9 C7-C8 40-45 100-110 D0 C8-C9

[0054] It is noted that the notations for swing weight matching, as indicated in the columns above in Tables II, and I are used universally today. As is standard, the weight distribution of each club of a designated set is completely specified. The balance arm of the conventional swing weight matching scale has alphabetically designated major divisions that are subdivided into numerical tenths so that the position of the poise on the balance arm has an alphanumeric designation such as C8, D0, etc. The balance position of the poise is the same for each club of the swing weight matched and the set is identified by the alphanumeric designation of this poise position. This alphanumeric designation is conventional, but will be used hereinafter to refer to the desired constant moment of inertia.

[0055] For testing in determining the correct flexural rigidity, the golfer hits a series of balls with the test clubs. During the hitting process, the golfer then selects the one club which provides the best feel and the best results in terms of distance, trajectory and direction of each shot. This will determine the frequency that is necessary for each set.

[0056] During the testing, the club head speed and/or distance is established. For testing speed, conventional machinery, such as a Swing Analyzer, produced by GOLFTEK, Inc., is used. For testing distance, a conventional driving range can be utilized.

[0057] Once the golfer has selected the best “felt” golf club in combination with the club that resulted in the best hit, the flexural rigidity is established; then using Table I or Table II, the swing weight is established. It is noted that the term “swing weight” is known in the field of golf. This swing weight is used in this invention for providing the selected constant moment of inertia.

[0058] In order to obtain maximum distance from any golf club, a golfer must be fitted with the maximum head weight with which he can generate the maximum club head speed. Once the club head speed is established, either by the use of a conventional swing analyzer or the use of the Tables above, and the ideal substantially constant moment of inertia is selected (labeled as the swing weight in the Tables above), the head weight for each club in the set can be precisely calculated to plus or minus 0.1 grams using the following formula for the substantially constant moment of inertia: $\begin{matrix} {{MI} = {{M_{h}\left( {L + d_{2}} \right)}^{2} + {\frac{1}{12}{M_{s}\left( L_{s} \right)}^{2}} + {\frac{1}{3}{M_{s}\left( \frac{L_{s} + d_{2}}{2} \right)}^{2}} + {M_{b}\left( {d_{1} + d_{2}} \right)}^{2}}} & (1) \end{matrix}$

[0059] where

[0060] MI=Selected Moment of Inertia (gm in²)

[0061] M_(h)=Mass of the head (grams)

[0062] L=Playing length of the club (in)

[0063] M_(s)=Mass of the shaft (grams)

[0064] L_(s)=Cut length of the shaft (inches)

[0065] M_(b)=Mass of the butt end including the grip (grams)

[0066] d₁=Distance from the center of M_(b) to the butt end of the shaft

[0067] d₂=Point above the end of the butt of the club used as the axis of rotation for the calculation of the moment of inertia.

[0068] Using equation (1) as defined above, the mass of the head can be solved by: $\begin{matrix} {M_{h} = \frac{{MI} - {\frac{1}{12}\left( M_{s} \right)\quad \left( L_{s} \right)^{2}} - {\frac{1}{3}\left( M_{s} \right)\quad \left( \frac{L_{s} + d_{2}}{2} \right)^{2}} - {M_{b}\left( {d_{1} + d_{2}} \right)}^{2}}{\left( {L + d_{2}} \right)^{2}}} & (2) \end{matrix}$

[0069] All the elements are known. For the calculation of this equation d₁ and d₂ can be assumed to be 2 inches. The respective head weights of the other golf clubs of the particular determined moment of inertia (swing weight) are then readily calculated. Once calculated, the club heads to be used are weighted to correspond to the calculated value for each club in the set. Using these weighted heads, the shafts are cut, as described above, to provide the designated flexural rigidity for each club in the set. The heads are then fixed to the corresponding shafts so that the final step, determining the center of gravity, can be completed.

[0070] Center of Gravity

[0071] In order to support the theory of consistent feel throughout a set of clubs, the center of gravity of each club must be set. The center of gravity of each club relates to the head weight, length, and force as applied by the golfer during the swing. As seen in FIG. 3, the center of gravity C for the clubs should be based on the amount of applied force F being a constant. Using the ideal club 10 as the base, which is typically the shortest club in the set, the force required to move the club can be calculated using the following equation:

FC=WL₁  (3)

[0072] wherein:

[0073] F=Force applied by the golfer

[0074] C=Distance to center of gravity from the butt end of the selected shortest club

[0075] W=Total weight of head and shaft

[0076] L₁=Club length L plus d₂

[0077] d₂=Point above the end of the butt of the club used as the axis of rotation

[0078] The point above the end of the butt of the club used as the axis of rotation (d₂) can be assumed to be 2 inches. Equation (3) can be rewritten for representing the Force by the following equation: $\begin{matrix} {F = \frac{{WL}_{1}}{C}} & (4) \end{matrix}$

[0079] The force is calculated for the base club. The base club is the shortest club of a set. Normally, for irons it is the wedge or 9 iron, while for woods it is the 5 wood or the shortest wood to be made. Accordingly, it is seen that total weight of the head and shaft is known (W), the total length of the club (L) plus the point above the end of the butt end of the club used as the axis of rotation (d₂) will give the known value for (L₁) wherein (d₂), if not measured, can be assumed to be two inches. The center of gravity C is measured for the shortest club. In order to do so, as seen in FIG. 4, the club 10 is placed on a conventional pedestal 26. If the club is leaning in a particular direction, or a first direction, the club is shifted in the opposite direction, or a second direction. The club is observed again to see if it is in balance or if it is leaning. If it is leaning, the club is shifted as discussed above. This process is repeated until the club is balanced on the pedestal. Once a balance or an equilibrium is achieved with the club at rest on the pedestal, a measurement is taken. This measurement C, as seen in the drawings, is taken from the butt end of the club to the point on the club which rests on the pedestal 26. This is known as the center of gravity (C). The force (F) can be calculated. Once the force has been established for the base club, the formula, as written in equation (4) is rewritten so that the center of gravity can be calculated for the clubs in the set, based on the force calculated for the base club. This equation for the center of gravity is defined as follows: $\begin{matrix} {C_{n} = \frac{W_{n}L_{n}}{F}} & (5) \end{matrix}$

[0080] wherein:

[0081] F=Force applied by the golfer on the shortest or base club

[0082] C_(n)=A calculated measurement measuring establishing a distance the butt end of club n of the set to the center of gravity of club n

[0083] W_(n)=Total weight of head and shaft of club n

[0084] L_(n)=The length of the club n plus d₂

[0085] This will allow for the center of gravity to be calculated for the rest of the clubs for n being the consecutive or particular club in the set. As the rest of the clubs are gripped, the center of gravity is set by adding the appropriate weight to the butt end of the club via conventional means as necessary to establish the center of gravity in the required location relative to the butt end of the club. Hence, the calculated C_(n) is the distance from the butt end of the club to the point on the club that will rest on the pedestal. If the club is leaning or tilting, appropriate weight is added, until the club is balanced on the pedestal.

[0086] This procedure has been found to provide the same feel to each club in the set while the constant frequency of each club in the set of Irons and Woods provides more consistent performance. Hence, it is seen that the center of gravity is inversely proportional to a force generated by the swing of the golfer.

[0087] The method for providing a matched set of clubs by providing equivalency between flexural rigidity, substantially constant moment of inertia, and center of gravity as defined below, is to first determine the appropriate flexural rigidity and then the substantially constant moment of inertia for the user by utilizing Table I or Table II as discussed above.

[0088] Hence, the golfer hits with preset test clubs from which the individual selects the club that feels the best. During this test either the person's club head speed (of the driver) or the distance that they hit (the 5 iron) can be established.

EXAMPLES Determination of Flexural Rigidity and Moment of Inertia

[0089] Example 1: A male golfer, who limits playing golf to approximately three to four times a month, hits a series of golf balls with a preset set of test clubs using the driver. The golfer felt that the test club having the precise frequency of 265 cycles per minute felt the best and provided the best results. His club head speeds were recorded at 79, 80, 82, and 83 MPH. Using Table 1 it is seen that ideal swing weight or moment of inertia would be a C7.

[0090] Example 2: A male golfer, who is a semi-professional, hits a series of golf balls with clubs from a preset set using the driver. The golfer felt that the test club having the precise frequency of 270 cycles per minute felt and performed the best. His club head speeds were recorded at 110, 112, 115, and 111 mph. Using Table 1, it is seen that the ideal swing weight or moment of inertia would be a C2. However, since this is a semi-professional golfer, the maximum swing weight or moment of inertia would be more beneficial. Hence, a C5 would be used.

[0091] Example 3: A female golfer, who plays regularly two to three times per week, hits a series of golf balls with a preset set of test clubs using the 7 irons and 5 irons. On completion of the test she has selected a 7 iron with a frequency of 290 cpm and a 5 iron with a frequency of 285 cpm. She then hits the 285 cpm 5 iron with a ¼ inch choked down grip, to shorten the club and stiffen the shaft, and finds the results and feel to be better than either of the first frequencies selected. She then hits the 285 cpm 7 iron choked down the same amount and confirms the feel and results are better. This added process establishes the ideal frequency established as 287 cpm. She then hits the 255 cpm driver choked down ¼ of an inch and finds the feel and performance to be very good. During this test the driver speed is recorded as 66, 65, 67, 63 mph and from Table II, her ideal swing weight or moment of inertia is seen to be C6.

[0092] Example 4: A right handed male golfer, who is a low handicap player hits a series of golf balls with a preset set of test clubs using the 7 and 5 irons. On completion of the test he has selected a 300 cpm 7 iron and a 295 cpm 5 iron. As cited in example 3, this indicates that his ideal frequency is between 295 and 300 cpm. To determine the precise frequency required, he is asked to draw (move right to left) the ball and to fade (move left to right) the ball in order to determine the best club. During this test the 295 cpm clubs (5 and 7 irons) both cause the ball to draw more than desired and produce only a slight fade. This indicates to the tester that the shaft frequency is too low. Similarly the 300 cpm 7 and 5 irons produce a very slight draw and an excessive fade. By choking down ¼ inch with the 295 cpm 7 and 5 irons he finds that he can control both the fade and the draw and finds that both clubs feel better. The ideal frequency is determined to be 297 cpm. During this second phase of the test it is noted that the average distance obtained with the 5 iron is 195 yards. From Table I his ideal swing weight or moment of inertia is C5.

[0093] Example 5: A 60-year-old male golfer, who plays regularly, hits a series of golf balls with a preset set of test clubs using the 7 and 5 irons. From the test the golfer indicated that the 305 cpm test clubs performed and felt better and selected 305 cpm as his preferred frequency. Subsequent testing with the drivers recorded club head speeds that averaged 83 mph. From Table I, his ideal swing weight or moment of inertia is C8.

[0094] Example 6: A 24-year-old male assistant professional hits a series of golf balls with a preset set of test clubs using the 7 and 5 irons. From the test he indicated that his preferred frequency was 295 cpm. Club head speed tests with the drivers record an average speed of 109 mph. From Table I, his ideal swing weight or moment of inertia is C4, which he used with great success.

EXAMPLES Determination of Center of Gravity for a Set of Golf Clubs

[0095] Example 7: Tabulated below is the recorded data for determining the center of gravity. The head weight and flexural rigidity has previously been determined. The club numbers (#), playing length, head weight, and shaft weight are all known elements. For determining the center of gravity for each club, (L₁) must be used. This length is defined as the length of the club (L) plus the distance to the point above the end of the butt end of the club used as the axis of rotation (d₂). For the purpose of this example, d₂ is assumed to be two inches. Thereby, (L₁) is also a known element. Accordingly, the center of gravity can easily be calculated for a set of clubs. The first step, however is to determine the force for the shortest club in a set. In the case of irons, this would be the 9 iron. The center of gravity for this 9 iron was measured at 28 inches. Therefore, the force F, measured in grams, can be calculated as shown below: Shaft Total Force Playing Head weight weight F = WL₁/C Club # Length L L₁ = L + d₂ weight M_(h) M_(s) W = M_(h) + M_(s) C = 28 in (irons) (inches) (inches) (grams) (grams) (grams) (grams) 9 35 37 302.0 67.64 369.64 488

[0096] Knowing the force F, the rest of the centers of gravity can be calculated for the irons. These calculations are shown below: CALCULATION FOR CENTER OF GRAVITY FOR IRONS Center of Shaft Gravity Playing Head weight Total weight C = WL₁/F Club # Length L L₁ = L + d₂ weight M_(h) M_(s) W = M_(h) + M_(s) F = 488 grams irons (inches) (inches) (grams) (grams) (grams) (inches) 8 35.5 37.5 292.9 68.63 361.53 27.8 7 36 38 284.2 69.62 353.82 27.6 6 36.5 38.5 275.8 70.60 346.40 27.5 5 37 39 267.7 71.60 339.30 27.4 4 37.5 39.5 260.0 72.60 332.60 26.9 3 38 40 252.5 73.60 326.10 26.7

[0097] Example 8: The same process can be used to find the center of gravity for woods. The first step, however, is to determine the force for the shortest club in a set. In this case, it would be a 7 wood. The centers of gravity for this 7 wood were measured at 30.5 from the butt end. Therefore, the force F, measured in grams, can be calculated as shown below: Shaft Total Force Playing Head weight weight F = WL₁/C Club # Length L L₁ = L + d₂ weight M_(h) M_(s) W = M_(h) + M_(s) C = 28 in (woods) (inches) (inches) (grams) (grams) (grams) (grams) 7 40.4 42.4 230.2 85.86 316.06 440.4

[0098] Knowing the force F, the rest of the center of gravity can be calculated for the woods. These calculations are shown below: CALCULATION FOR CENTER OF GRAVITY FOR WOODS Center of Gravity Shaft C = WL₁/F Playing Head weight Total weight F = 440.4 Club # Length L L₁ = L + d₂ weight M_(h) M_(s) W = M_(h) + M_(s) grams (woods) (inches) (inches) (grams) (grams) (grams) (inches) 5 41.5 43.5 217.8 88.0 305.8 30.2 3 42.5 44.5 206.3 89.1 295.4 29.8 1 43.5 45.5 195.3 92.34 287.6 29.7

[0099] Tolerance

[0100] It is noted that if the butt end of the shaft is cut or the mass of a head is adjusted, then the Moment of Inertia for the club will change. However, in either of these processes the change is so small that the constant moment of inertia will have an acceptable tolerance within which it would be considered a constant.

[0101] In summary, M_(b) is mass added to the butt end including the grip and weight required locating the center of gravity at its calculated position for each club using the base club method. However, this added weight used for determining the center of gravity is normally insignificant.

[0102] A constant moment of inertia must have an acceptable tolerance within which it would be considered a constant. The moment of inertia is selected based on the swing weight of a base club in a set of test clubs. As seen, this set of test clubs is made up of eight drivers covering a range of swing weights from very light to very heavy. The selected swing weight, which is the heaviest head that creates the highest swing speed, is then converted to a moment of inertia using Table A, as defined below. TABLE A Conversion Swing Weight MI Variation Item (gm in) (gm in²) (gm in²) 1 B8 457617 2 B9 460596 2979 3 C0 463575 2979 4 C1 466554 2979 5 C2 469532 2978 6 C3 472511 2979 7 C4 475489 2978 8 C5 478468 2979 9 C6 481447 2979 10 C7 484426 2979 11 C8 487405 2979 12 C9 490384 2979 13 D0 493363 2979 14 D1 496342 2979 15 D2 499321 2979

[0103] Once the moment of inertia is determined, the user will use Equation 1 for calculated the head weight. The swing weight is related to the clubhead speed, which is clearly illustrated in Table II.

[0104] As seen in the example above, a player who had an average speed of 83 mph and an ideal Swing Weight of C7 was selected from Table 1. This selected Swing Weight can be converted to a moment of inertia, as seen in Table A. It is noted that the notations for swing weight matching, as indicated in the column II above, and as indicated in the in Tables I and II are universally known, but have not previously been related to clubhead speed as detailed in this invention.

[0105] As seen in the table above, the variation of one swing weight is equivalent to 2979 gm in², for example, 460596-457617=2979.

[0106] Considering that a change of one swing weight, in head weight, is equal to a change of 1 cpm in the frequency of the shaft and that our objective is to maintain a set of clubs within plus or minus 1 cpm, an acceptable tolerance in the moment of inertia would be plus or minus 2979 gm in².

[0107] The actual change to the moment of inertia caused by the addition of the butt weight is related to the last part of equation (1) identified in the specification, specifically, M_(b)(d₁+d₂)². Assuming d₁ and d₂ are each equal to 2 and using an average value of M_(b) as 80 grams, wherein 50 grams is the weight of the grip, the maximum change in the moment of inertia would be:

MI=80(2+2)²=80(16)=1280 gm in²

[0108] This is well within what is considered acceptable tolerance. In actual practice, the 50 gram weight of the grip is included in the original calculation of MI; therefore, the real change to the selected MI is given by:

MI=(80−50)(2+2)²=30(16)=480 gm in²

[0109] Of the acceptable tolerance (section labeled variation), it is seen that the moment of inertia fall within this range, and is actually only 16% of the acceptable tolerance—480/2979×100=16.00%.

[0110] It can further be calculated that the total change in the moment of inertia is approximately 0.1 percent—480/484426×100=0.1%. This minute amount would not be noticeable to the golfer and will not affect the performance of the golf club. Hence, the addition of the weight on the butt end does not drastically affect the moment of inertia, and in fact, is considered insignificant.

[0111] As can be seen, the additional weight would not significantly change the moment of inertia and that this added weight is insignificant for determining the moment of inertia, but it is significant for achieving a center of gravity.

[0112] Process

[0113] The process of providing a matched set of clubs, wherein each club in a set includes the same feel and performance, a constant flexural rigidity of each complete iron and each complete wood, substantially constant moment of inertia for each iron and each wood, and the center of gravity as they relate to the swing of the individual golfer, will inherently optimize the performance of the golfer. This process is summarized below:

[0114] (a) finding the best “felt” club for determining the proper flexural rigidity. In this step, the golfer swings a series of preset test clubs and decides which one feels the best and provides the best performance. The frequency of the club that felt the best is recorded.

[0115] (b) Select the length of the club.

[0116] (c) From a series of preset test clubs the distance and/or speed is recorded.

[0117] (d) Calculate the Moment Of Inertia using equation (1)

[0118] (e) Calculate the other head weights using equation (2) and adjust the head weights to match.

[0119] (f) With all but taper tip shafts, stepped or un-stepped, set the required frequency for each club in the set by tip trimming. For Taper tips shafts a minimum amount of tip trimming, up to 0.5 inches is possible to adjust the frequency or a change in headweight of two to three grams can be made without affecting the required Moment of Inertia. There must be an allowable deviation (a tolerance) from the calculated head weight. It use be realized that the selected Moment of Inertia is also a number which must have an acceptable tolerance. Based on a golfer's ability to detect changes in the Moment of Inertia it has been determined that a 1% change in the Moment of Inertia, which equate to about three grams in head weight, will not be detectable by the golfer; therefore a substantially constant Moment of Inertia is what is achieved. The exact frequency is the most importance consideration and minor adjustments to the frequency can be made by either tip trimming the shaft or adjusting the weight of the head before the shaft is butt cut to length, which can be done after the required frequency is obtained.

[0120] (g) Select the base club and install the grip. Normally this club does not have weight added.

[0121] (h) Measure the Center of Gravity and calculate the Force (F) using equation (4).

[0122] (i) Using equation (5) calculate the location of the center of gravity for each club in the set.

[0123] (j) Install the grips on the rest of the set as the total weight of each club is made the same as the base club. The center of gravity is set by locating the added weight inside the butt end of the club so that the center of gravity is in the proper location on each club after the grip is installed.

[0124] It is noted that the process defined above has worked well on all types and styles of conventional shafts. Consequently providing a method that can work for both tapered and parallel shafts.

[0125] While the invention has been particularly shown and described with reference to an embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention. 

We claim:
 1. A correlated set of golf clubs for use by a golfer, said correlated set of golf clubs comprising: at least two golf clubs of an equivalent set; each club includes a shaft having a first end and a butt end; a head being located at said first end and a grip being located at said butt end; said head having a head weight; said plurality of shafts lengths decreases as said head weights increases; each club has a measured frequency when said head and said grips are attached thereto; said measured frequency of said plurality of clubs being within plus or minus 1 cycle per minute of each other; and wherein said measured frequency is established by butt-cutting said butt-end of said shaft, said butt-cutting is continued until measured frequency equals the established required frequency for the length of each club in the set being built.
 2. A correlated set of golf clubs as in claim 1, wherein each club has a swing weight which produces an optimum hit, said swing weight represents a moment of inertia (MI), each of said shafts includes said head weight (M_(h)), each of said clubs includes a playing length (L), each of said shafts includes a weight (M_(s)), each butt end includes a weight(M_(b)), and said head weight (M_(h)) being represented by: ${M_{h} = \frac{{MI} - {\frac{1}{12}\left( M_{s} \right)\quad \left( L_{s} \right)^{2}} - {\frac{1}{3}\left( M_{s} \right)\quad \left( \frac{L_{s} + d_{2}}{2} \right)^{2}} - {M_{b}\left( {d_{1} + d_{2}} \right)}^{2}}{\left( {L + d_{2}} \right)^{2}}};$

for d₁ being a distance from a center of said butt weight to said butt end of said grip and d₂ being a point above said butt end of club used as the axis of rotation.
 3. A correlated set of golf clubs as in claim 2 wherein d₁ and d₂ are equal to 2 inches.
 4. A correlated set of golf clubs as in claim 1 wherein said shafts are stepped with either parallel or tapered tips.
 5. A correlated set of golf clubs as in claim 1 wherein tip ends of said shafts are either parallel or taper tip in formation and said shafts are free from step formation.
 6. A correlated set of golf clubs as in claim 1, wherein said club has a moment of inertia and said moment of inertia is substantially constant for each club and is related to the club head speed generated by the golfer.
 7. A correlated set of golf clubs as in claim 1 wherein said set of golf clubs includes a base club, said base club is a completed club and includes a first length, said first length is the shortest length in said set of golf clubs, a force (F) is calculated for said base club using the following equation: ${F = \frac{{WL}_{1}}{C}};$

wherein: C is a measured distance from the center of gravity of said base club to said butt end of said club; W is a total weight of said head and said shaft of said base club; L₁ is said first length plus d₂ for d₂ being a point above said butt end of said grip of said base club used as the axis of rotation; a center of gravity is calculated for each additional club of said set using the following equation: ${C_{n} = \frac{W_{n}L_{n}}{F}};$

wherein C_(n) is a calculated measurement establishing a distance from said butt end of club n of said set to said center of gravity of club n; W_(n) is a total weight of said head and said shaft of said club n; L_(n) is a length of said club n plus d₂ for d₂ being a point above said butt end of said grip of said club n used as the axis of rotation; and F is the calculated force applied by the golfer.
 8. A method of matching a correlated set of golf clubs to a particular golfer, wherein each club has a same feel for said particular golfer, each golf club in the set has a different length and includes a shaft having a butt end and a head end, and said head end has a head, said method comprising: (a) finding a club of the best performance and which a particular golfer determines as a club which feels the best from a set of preset test clubs for determining a proper flexural rigidity; (b) recording a frequency from said best felt club; (c) establishing a best swing weight; (d) recording said swing weight for conversion to a moment of inertia; (e) calculating a head weight (M_(hn)) using said moment of inertia MI for each club by the equation: ${M_{h} = \frac{{MI} - {\frac{1}{12}\left( M_{s} \right)\quad \left( L_{s} \right)^{2}} - {\frac{1}{3}\left( M_{s} \right)\quad \left( \frac{L_{s} + d_{2}}{2} \right)^{2}} - {M_{b}\left( {d_{1} + d_{2}} \right)}^{2}}{\left( {L + d_{2}} \right)^{2}}};$

where, L_(n) is a playing length of club n, M_(sn) is a shaft weight of club n, M_(bn) is a weight, including said grip added to said shaft for a butt end of club n, L_(sn) is a length of a shaft of club n, for d_(1n) being a distance from a center of said butt weight to said butt end of said grip and d₂ being a point above said butt end of said club n used as the axis of rotation; (f) butt-cutting said club to obtain a required length and assembling each club by attaching a head to a first end of a shaft and measuring an assembled frequency; and (g) adjusting said assembled frequency to equal said required frequency by adjusting head weight and continuing butt-cutting of said club until said assembled frequency is equal to said recorded selected frequency.
 9. A method as in claim 10 wherein there is provided the further steps of: (h) selecting a base club, said base club includes a first length; (i) calculating a force (F) for said base club using the following equation: ${F = \frac{{WL}_{1}}{C}};$

wherein: C is a measured distance from a center of gravity of said base club to said butt end of said base club; W is a total weight of said head and said shaft of said base club; L₁ is said first length plus d₂ for d₂ being a point above said butt end of said grip of said base club used as the axis of rotation; (j) calculating a center of gravity for each additional club of said set using the following equation: ${C_{n} = \frac{W_{n}L_{n}}{F}};$

wherein C_(n) is a calculated measurement establishing a distance from said butt end of club n of said set to said center of gravity of club n; W_(n) is a total weight of said head and said shaft of said club n; and L_(n) is a length of said club n plus d₂ for d₂ being a point above said butt end of said grip of said club n used as the axis of rotation; and F is the calculated force applied by the golfer.
 10. A method of designing a correlated set of golf clubs for use by a golfer, wherein each club has a same feel, each golf club in the set has a different length and includes a shaft having a butt end and a first end, and said first end has a head and said butt end includes a grip, said method comprising: (a) establishing a required frequency for an assembled golf club [by butt-cutting a butt end of each club for establishing a proper club length; and]; (b) butt-cutting establishes an assembled frequency; and (c) adjusting said assembled frequency to equal said required frequency by continuing butt-cutting and adjusting the head weight of said club until said assembly frequency is equal to said recorded selected frequency.
 11. A method as in claim 10 wherein there is provided the further step of correlating each club to have substantially a constant moment of inertia.
 12. A method as in claim 10 wherein there is provided the further step of calculating a center of gravity which is inversely proportional to a constant swing force of a golfer, and said center of gravity for each club includes a constant force.
 13. A method as in claim 10 wherein there is provided the further steps of: (d) providing a grip on said butt end and establishing a swing weight which produces an optimum hit and said swing weight represents a moment of inertia (MI); (e) calculating a head weight (M_(hn)) for each club by the equation: ${M_{h} = \frac{{MI} - {\frac{1}{12}\left( M_{s} \right)\left( L_{s} \right)^{2}} - {\frac{1}{3}\left( M_{s} \right)\left( \frac{L_{s} + d_{2}}{2} \right)^{2}} - \left( {M_{b}\left( {d_{1} + d_{2}} \right)} \right)^{2}}{\left( {L + d_{2}} \right)^{2}}};$

where, L_(n) is a playing length of club n, M_(sn) is a shaft weight of club n, M_(bn) is a weight for said butt end of club n, L_(sn) is a length of a shaft of club n, for d_(1n) being a distance from a center of said butt weight to said butt end of said grip and d₂ being a point above said butt end of club n used as the axis of rotation.
 14. A method as in claim 10 wherein there is provided the further steps of: (d) selecting a base club, said base club includes a first length; (e) calculating a force (F) for said base club using the following equation: ${F = \frac{{WL}_{1}}{C}};$

wherein: C is a measured distance from a center of gravity of said base club to said butt end of said club; W is a total weight of said head and said shaft of said base club; L₁ is said first length plus d₂ for d₂ being a point above said butt end of said grip of said base club used as the axis of rotation; (e) calculating a center of gravity for each additional club of said set using the following equation: ${C_{n} = \frac{W_{n}L_{n}}{F}};$

wherein C_(n) is a calculated measurement establishing a distance from said butt end of club n of said set to said center of gravity of club n; W_(n) is a total weight of said head and said shaft of said club n; and L_(n) is a length of said club n plus d₂ for d₂ being a point above said butt end of said grip of said club n used as the axis of rotation; and F is the calculated force applied by the golfer.
 15. A method as in claim 12 wherein said shafts are stepped with either parallel or tapered tips.
 16. A method as in claim 12 wherein tip ends of said shafts are either parallel or taper tip in formation and said shafts are not stepped.
 17. A method of matching a correlated set of golf clubs as in claim 1 wherein said shafts are fabricated from wood, steel, graphite, or any material used for fabricating conventional golf clubs. 